The present invention relates to a novel and improved electric connector of the alternate stratification type of layers of electrically conductive and insulating rubbery materials shaped, for example, in an elongated rod-like form having a rectangular cross section which is used for electrically connecting two circuit boards or the like electronic units by contacting under pressure as held therebetween. More particularly, the invention provides an elastomeric connector of the stratification type having a rectangular cross section, two or more of the connectors of this type being readily assembled and integrated together into one connector having an irregular cross section by being put together side by side. That is, a composite connector having an irregular cross section, e.g. L-shaped, U-shaped, T-shaped or the like cross section, can readily and conveniently be obtained by combining two or more of the unit connectors of the invention and conventional connectors each having a rectangular cross section as if to play with building blocks.
Needless to say, many of the electronic instruments in recent years such as electronic watches, pocketable electronic calculators and the like are assembled with one or more of electric connectors which serve to establish electric connection between two circuit units as between a liquid crystal display unit and a driving circuit board thereof. Such an electric connector is used as being held between the opposite contacting terminal portions of the circuit units with an appropriate contacting pressure.
Among a variety of the types of the electric connectors used for such a use, the most widely used ones are those of the so-called elastomeric stratification type. An electric connector of this type has an elongated rod-like form composed of alternate stratification in the longitudinal direction of the rod with a plurality of layers of electrically conductive and insulating rubbers so that the connector as a whole has a zebra-like appearance on the lateral surfaces and an electroconductivity within the plane perpendicular to the longitudinal direction of the elongated rod but is electrically insulating in the longitudinal direction thereof. Most of the connectors of this type are shaped in a rod-like form having a square of rectangular cross section although connectors having a circular or elliptic cross section are sometimes used according to need.
The connector is used as sandwiched between the oppositely facing contacting terminal portions on two circuit units with an appropriate contacting pressure. When the contacting terminal portions on two circuit units are at the positions just to face oppositely one to the other, the above mentioned connectors having a simple cross section, e.g. square, rectangular, circular or elliptic cross section, can be used with no problems in respect of the cross sectional configuration. When it is desired, however, to electrically connect two contacting terminal portions of the circuit units at somewhat slided positions from each other, a connector of a simple cross section can no longer be used and it is sometimes necessary to use a connector having an irregular cross section such as L-shaped, T-shaped, E-Shaped, U-shaped or the like cross section.
In the prior art, such an electric connector of the stratification type having an irregular cross section is manufactured by integrally molding by use of a metal mold of the desired form or, alternatively, by bonding together adhesively two or more of the connectors of stratification type each having a rectangular cross section side by side to give a desired irregular cross section. The former method is, however, disadvantageous due to the troublesome steps of fabrication resulting in a high production cost of the connector as well as due to the relatively low accuracy in the dimensions of the connector while the latter method is sometimes defective because the electric connection between the unit connectors bonded together is not always very reliable. Further alternatively, an elastomeric connector of stratification type prepared to have a simple cross section, e.g. rectangular cross section, is cut and engraved longitudinally to have a desired irregular cross section but this method must be carried out by handworks using a special jig and is too time- and labor-consuming so that the method is entirely unsuitable for the industrial manufacture of electric connectors having an irregular cross section.
Therefore, none of the prior art methods has been satisfactory when an elastomeric electric connector of the stratification type having an irregular cross section with high performance is to be manufactured with good productivity from the industrial standpoint.